1. Field of the Invention
This invention relates to a quench station and a method for quenching formed glass sheets in a manner that can reduce cycle time and thus increase production.
2. Background Art
Systems for forming glass sheets by heating and then quenching the glass sheets to provide toughening have cycle times whose shortening can be limited by the length of time required to perform the quenching. The quenching is performed by quenching gas that is directed to opposite surfaces of the formed glass sheet to provide a temperature differential between the surfaces and the glass center. That temperature differential must remain throughout the cooling until reaching ambient temperature or the glass will not be toughened by providing compression of its surfaces and tensioning of its center.
U.S. Pat. No. 4,361,432 McMaster et al. discloses glass sheet quenching between lower and upper quench heads with the formed glass sheet on an open center ring and, upon completion of the quenching, the downwardly directed quenching gas from the upper quench head is terminated to lift the glass sheet upwardly from the open center ring against the upper quench head to permit the ring to be moved to start another cycle. A delivery ring is moved under the formed glass sheet and the downwardly directed gas is again supplied to deposit the glass sheet on the delivery ring for delivery when the next formed glass sheet is moved to between the lower and upper quench heads for the quenching.
One object of the present invention is to provide an improved quench station for quenching formed glass sheets.
In carrying out the above object, the quench station for quenching formed glass sheets in accordance with the invention includes a first quench section having lower and upper quench head assemblies for respectively supplying upwardly and downwardly directed quenching gas to a formed glass sheet therebetween to provide partial quenching of the glass sheet. Such partial quenching is insufficient without further forced cooling in addition to natural convection to prevent the loss of the glass temperature differentials that toughens the glass upon finally cooling to ambient temperature. A second quench section of the quench station has lower and upper quench head assemblies for respectively supplying upwardly and downwardly directed quenching gas to the partially quenched glass sheet upon being received therebetween to complete the quenching of the glass sheet. A shuttle of the quench station is movable in a transfer direction simultaneously with respect to a forming station where the glass sheet is formed, the first quench section and the second quench section to provide glass sheet transfer. The shuttle has three glass positions so as to be capable of simultaneously transferring three glass sheets upon each movement in the transfer direction. Three glass sheets are thus simultaneously moved from the forming station to the first quench section, from the first quench section to the second quench section, and from the second quench section for delivery. A control of the quench station supplies quenching gas to the upper and lower quench sections of the first and second quench sections to force the glass sheets upwardly from the shuttle against the upper quench head assemblies and permit movement of the shuttle in the opposite direction to the transfer direction in preparation from the next cycle.
The construction of the quench station includes a framework, and the lower and upper quench head assemblies of each quench section each includes a plurality of quench heads through which pressurized gas is delivered. The quench heads of each quench head assembly are adjustable with respect to each other to permit quenching of different shapes of formed glass sheets. The lower and upper quench head assemblies respectively include lower and upper templates mounted on the framework to position the quench heads thereof in the proper position for the glass sheet shape to be quenched. Adjusters of the quench station adjust the locations of the templates on the framework to properly position the quench heads. Clamps secure the templates with respect to the framework, with the clamping being provided after the adjustment provided the adjusters.
The lower and upper quench head assemblies respectively include lower and upper linkages for connecting their quench heads. Lower and upper quench head actuators respectively extend between the framework and the lower and upper quench head assemblies to provide adjusting movement of the quench heads under the control of the linkages in preparation for positioning the quench head assemblies by the lower and upper templates.
Each of the upper quench head assemblies includes thermally insulative stops against which the glass sheets are forced upwardly by the upwardly directed quenching gases during the cyclical operation of the quench station.
Another object of the present invention is to provide an improved method for quenching formed glass sheets.
In carrying out the immediately preceding object, the method for quenching formed glass sheets in accordance with the invention is performed by moving a first formed glass sheet on a shuttle from a forming station to a first quench section having lower and upper quench head assemblies for respectively supplying upwardly and downwardly directed quenching gas to provide partial quenching thereof which is insufficient without further forced cooling in addition to natural convection to prevent loss of the glass temperature differential that toughens the glass upon finally cooling to ambient temperature. Simultaneously with the movement of the first formed glass sheet, a second partially quenched formed glass sheet is moved on the shuttle from the first quench section to a second quench section having lower and upper quench head assemblies for respectively supplying upwardly and downwardly directed quenching gas to the partially quenched glass sheet upon being received therebetween to complete the quenching of the second glass sheet. Simultaneously with the movement of the first and second glass sheets a third fully quenched glass sheet is moved from the second quench station for a final cooling to ambient temperature. The flow of the quenching gas from the lower and upper quench head assemblies of the first and second quench sections is controlled to move the formed glass sheet upwardly from the shuttle after movement thereto on the shuttle and thereby permits reverse movement of the shuttle in preparation for another cycle. Subsequently the flow of the quenching gas from the lower and upper quench head assemblies of the first and second is controlled to move the formed glass sheets downwardly onto the shuttle to permit another cycle of transferring three formed glass sheets from the forming station to the first quench section, from the first quench section to the second quench section, and from the second quench section for final cooling.
In performing the quenching method, the lower and upper quench head assemblies are respectively positioned by lower and upper templates, and the lower and upper templates are adjusted with respect to a framework of the quench sections and are clamped with respect to the framework to position the lower and upper quench head assemblies. Furthermore, the quench heads of the lower and upper quench head assemblies are respectively connected by lower and upper linkages and are moved by associated actuators for positioning in preparation for use.
During the quenching, the glass sheets are forced upwardly against thermally insulative stops of the upper quench head assemblies.